import math

if __name__ == '__main__':
    x1, y1, x2, y2 = [float(i) for i in input().split()]
    d = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
    print("{0:.5f}".format(d)) import math math if __name__ == '__main__':
    x1, y1, x2, y2 = [float(i) for i in input().split()]
    d = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
    print("{0:.5f}".format(d)) __name__ == '__main__' __name__ '__main__' float(i) for i in input().split() for i in input().split() i input().split() ().split () input split for i in input().split() float(i) float i x1, y1, x2, y2 = [float(i) for i in input().split()] x1 [float(i) for i in input().split()] y1 x2 y2 d = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2) d math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2) math.sqrt math sqrt (x1 - x2) ** 2 + (y1 - y2) ** 2 (x1 - x2) ** 2 x1 - x2 x1 x2 2 (y1 - y2) ** 2 y1 - y2 y1 y2 2 print("{0:.5f}".format(d)) print "{0:.5f}".format(d) "{0:.5f}".format "{0:.5f}" format d x1, y1, x2, y2 = [float(i) for i in input().split()] [float(i) for i in input().split()] x1 y2 = [float(i) for i in input().split()] [float(i) for i in input().split()] y2 x2, y2 = [float(i) for i in input().split()] [float(i) for i in input().split()] x2 y1, x2, y2 = [float(i) for i in input().split()] [float(i) for i in input().split()] y1 d = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2) math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2) d
import math

if __name__ == '__main__':
    x1, y1, x2, y2 = [float(i) for i in input().split()]
    d = math.sqrt((x1 - x2) ** 2 + (y1 - y2) ** 2)
    print("{0:.5f}".format(d))